1. Field of the Invention (Technical Field)
The present invention relates to removing particulate and dissolved solids from water by spiral wrapped membrane elements utilizing a dual diaphragm pump system that preferably incorporates pressure recovery, pulsing, fixed recovery (ratio of permeate to feed), and thin feed spacer spiral wrapped membrane elements. The maximum benefit of the system is achieved when reverse osmosis (“RO”) is utilized as the membrane technology due to the high pressures inherent in RO membrane processes. However, the system of the present invention is also effective on microfiltration, ultrafiltration, nanofiltration, and other membrane systems. More particularly the present invention relates to alternative means to increase the production of potable water per unit size of membrane element and to reduce the energy cost per unit volume of water treated.
The present invention further relates to a reverse osmosis hand held pump with pressure recovery and in-line components for easy fabrication.
2. Background Art
Removing impurities from drinking water supplies is a major factor in reducing the health risks to the human population. High levels of total dissolved solids (TDS) in water, such as dissolved salts in seawater, make the water unfit for drinking because of the ion imbalance in the human system. Most drinking water in the world today comes from ground or surface water sources and potable water from these sources is produced at small and large municipal drinking water treatment plants. A very small percentage of drinking water is produced from de-salination facilities. There are many settings in which these large systems are not practical. For example, campers, military personnel, and disaster relief situations require small man-portable systems that can treat water from just about any water source to produce potable water. To be effective in such remote settings, a system must be capable of repeated operation with little operator skill, no external power sources, and very little maintenance.
To be fully comprehensive, water filtration must include the capability for both conventional filtration as well as desalination. Conventional filtration can remove particulates that cause turbidity such as dirt, silt, sand, and larger organisms such as Giardia and Cryptosporidium. Reverse osmosis (“RO”) technology must also be included to remove ions from such sources as sea water. At sea water concentrations of 35,000 milligrams per liter (mg/L), the system must be effective enough to remove ions to levels less than 1000 mg/L. While sodium and chloride are the two ions of concern in sea water, the system must be able to remove other ions as well. All of these ions are collectively known as TDS.
Existing technology removes TDS utilizing RO technology. Manual pumps utilize a pressure recovery feature to reduce the applied force required to generate the pressure needed to drive the RO process. U.S. Pat. No. 3,749,524, to Jordan, entitled “Manually Operated Pump Utilizing Backpressure for Easement of Pump Stroke,” discloses a pressure recovery feature for a pneumatic application. This feature does not apply to fluids such as water and lacks an efficient valve system for retentate discharge and for isolating the RO element in the event that TDS removal is not required. U.S. Pat. No. 4,124,488 to Wilson, entitled “Water Purification by Reverse Osmosis,” and U.S. Pat. No. RE 33,135, to Wanner, Sr. et al, entitled “Pump Apparatus,” disclose a reverse osmosis pump mechanism with a pressure recovery feature. The present invention addresses the current problems by incorporating a simple valve mechanism for retentate discharge.
U.S. Pat. No. RE 32,144, to Keefer, entitled “Reverse Osmosis Method and Apparatus,” discloses a pump mechanism with pressure recovery and accumulator for reverse osmosis. The mechanism does not incorporate an efficient pressure relief and retentate discharge mechanism integral to the piston and rod assembly.
U.S. Pat. No. 5,496,466, to Gray, discloses a portable water purification system with a double piston pump comprising a feed water piston in a feed water cylinder, a concentrate pumping section for removing concentrate from concentrate output, and a concentrate pumping section including a concentrate cylinder and piston wherein the pistons move in opposite axially directions. Gray does not teach differential pressure control or use of a spring or other mechanism for storing energy to average out the forces of the respective strokes. Further, Gray teaches use of a two-piston system only.
U.S. Pat. No. 5,503,736, to Schoenmeyr, discloses a booster pump for a reverse osmosis water purification system wherein the pump has a spring return piston stroked by the pressure of feedwater and a pair of solenoid control valves (controlled by a piston position detector switch) that control the flow of feedwater into and out of the pump to move the piston between stroke and return positions. The Schoenmeyr patent, while disclosing a single piston, employs a two-headed piston with solenoid control valves and a control circuit system, unlike the differential pressure activated valve of the present invention.
Additional tangentially related prior art includes: U.S. Pat. No. 5,589,066, to Gray; U.S. Pat. No. 5,865,980 to Patapoff et al.; U.S. Pat. No. 3,966,364, to Bachle et al.; U.S. Pat. No. 5,531,887, to Miers; U.S. Pat. No. 4,740,301, to Lopez; and U.S. Pat. No. 3,830,372, to Manjikian.